package cn.nubia.admin.common.shiro.util;


import org.springframework.asm.*;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

/**
 * <p>
 * <font color="red">依赖javassit</font>的工具类，获取方法的参数名
 * </p>
 * 
 * @author dixingxing
 * @date Apr 20, 2012
 */
public class Classes {private Classes() {
}

    /**
     *
     * <p>比较参数类型是否一致</p>
     *
     * @param types asm的类型({@link Type})
     * @param clazzes java 类型({@link Class})
     * @return
     */
    private static boolean sameType(Type[] types, Class<?>[] clazzes) {
        // 个数不同
        if (types.length != clazzes.length) {
            return false;
        }

        for (int i = 0; i < types.length; i++) {
            if(!Type.getType(clazzes[i]).equals(types[i])) {
                return false;
            }
        }
        return true;
    }


    /**
     *
     * <p>获取方法的参数名</p>
     *
     * @param m
     * @return
     */
    public static String[] getMethodParamNames(final Method m) {
        final String[] paramNames = new String[m.getParameterTypes().length];
        final String n = m.getDeclaringClass().getName();

        final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
        ClassReader cr = null;
        try {
            InputStream is = m.getDeclaringClass().getClassLoader().getResourceAsStream(n.replace('.', '/')+ ".class");
            cr = new ClassReader(is);
        } catch (IOException e) {
            e.printStackTrace();
            return new String[0];
        }
         cr.accept(new ClassVisitor(Opcodes.ASM5, cw) {
             @Override
             public MethodVisitor visitMethod(final int access,
                                              final String name, final String desc,
                                              final String signature, final String[] exceptions) {
                 final Type[] args = Type.getArgumentTypes(desc);
                 // 方法名相同并且参数个数相同
                 if (!name.equals(m.getName())
                         || !sameType(args, m.getParameterTypes())) {
                     return super.visitMethod(access, name, desc, signature,
                             exceptions);
                 }
                 MethodVisitor v = cv.visitMethod(access, name, desc, signature,
                         exceptions);
                 return new MethodVisitor(Opcodes.ASM4, v) {
                     @Override
                     public void visitLocalVariable(String name, String desc,
                                                    String signature, Label start, Label end, int index) {
                         int i = index - 1;
                         // 如果是静态方法，则第一就是参数
                         // 如果不是静态方法，则第一个是"this"，然后才是方法的参数
                         if (Modifier.isStatic(m.getModifiers())) {
                             i = index;
                         }
                         if (i >= 0 && i < paramNames.length) {
                             paramNames[i] = name;
                         }
                         super.visitLocalVariable(name, desc, signature, start,
                                 end, index);
                     }

                 };
             }
         }, 0);
        return paramNames;
    }

}